This invention relates to a device for evacuating an inlet to a water jet unit that is turned off wherein the water jet unit is disposed in a ship hull having a plurality of driving mechanisms. More particularly, the invention relates to a member that is movably engaged to a bottom of a ship hull. When the ship hull is in operation, the member is immersed into the relative water flow in front of the inlet of the driving mechanism. The configuration of the member is such that the water flow is deflected so that a cavity is formed in front of the intake opening to cover the same. In this way, water is prevented from flowing in through the intake. Additionally, the inlet of the turned off driving mechanism is drained. The present invention also relates to the use of such a deflection mechanism for this purpose and a method for draining the inlet of the turned off water jet unit while the ship hull is in operation.
Fast moving ship hulls are more often equipped with multiple driving mechanisms which often include the water jet units. Thus, there are many ships today that have up to four driving units. These are designed for velocities which often exceeds 40 knots so that it is easy to realize the need for maintaining the economy of operation while cruising at a lower velocity for example, in an archipelago or during night cruises when the passengers desire a smooth cruising speed.
The driving mechanisms are generally constructed to provide a good output at a high efficiency at the cruising speed which the ship is designed for. Therefore, if the effect of the output is reduced then the economy of operation is also reduced. It is therefore often more advantageous to completely turn off one of many units and to operate the remaining units at a constant output. This cannot be done without causing certain drawbacks such as increased resistance and vibrations. Besides the resistance caused by the impellent disposed in the turned off water jet units, the water flow through the intake is also undesirable and unnecessary due to increased weight which may be substantial. These drawbacks are obviously more apparent when one of the driving mechanisms have broken down and it is desirable to operate the ship at an acceptable cruising speed.
One objective of the present invention is to remove some of the above mentioned drawbacks by providing a deflection member that is movable and continuously adjustable and disposed in front of or adjacent to a forward edge of the intake. The deflection member creates a cavity defined in-the water that is outside the intake and covers the same. Thus, the penetration of water is prevented and the channel is drained so that any resistance from an idle impellent is eliminated. Additionally, the deflection member provides reduced weight and a corresponding reduced resistance to forward movement.
The objective is satisfied by the deflection member described in the appended claims.